Measurements from the MF spaced antenna mode radar at Scott Base (78°S, 167°E) include an estimate of the autocorrelation time scale (T0.5) of the scatterers, corrected for advection by the mean wind. Summer observations (December 1983) show a semidiurnal variation of T0.5. At heights of 87–95 km the minimum values of T0.5 occur when the zonal component of the semidiurnal tide is at its westward maximum. If it is assumed that decreasing values of T0.5 are associated with increasing turbulence, then these results are consistent with those of Balsley et al. (1983), who proposed that enhanced turbulence is generated in summer by low-frequency gravity waves and tidal components above the polar mesopause.